1. Field of the Invention
The present invention relates to a rotary pump that sucks and discharges a fluid and to a brake device in which the rotary pump is provided, the present invention being particularly suitable for application to an internal gear pump such as a trochoid pump or the like.
2. Description of the Related Art
An internal gear type of rotary pump, such as a trochoid pump or the like, is configured from an inner rotor that is provided with an external tooth portion on its outer circumference, an outer rotor that is provided with an internal tooth portion on its inner circumference, a casing that houses the inner rotor and the outer rotor, and the like. The inner rotor and the outer rotor are disposed within the casing in a state in which the internal tooth portion and the external tooth portion mesh with one another such that a plurality of chambers is formed by the teeth.
A structure for this sort of rotary pump has been disclosed in which, in an inner wall surface of the casing, grooves are formed that correspond to end faces of the outer rotor and the inner rotor, and seal members are disposed within the grooves, the seal members pressing against the end faces of the outer rotor and the inner rotor (refer to Japanese Patent Application Publication No. JP-A-2000-355274). Openings in the inner wall surface of the casing and the end faces of the outer rotor and the inner rotor are thus sealed between a high pressure location and a low pressure location, preventing a brake fluid leak from the high pressure location to the low pressure location.
However, with the known seal structure that is described above, the seal surface pressure tends to increase, and the brake fluid pressure increases excessively within a closed portion among the plurality of chambers that is not continuous with either one of a suction port and a discharge port. This creates a problem in that, when the brake fluid is discharged from the discharge port while the closed portion is continuous with the discharge port, a discharge pulsation increases, which in turn increases noise. An additional problem is created in that the excessive increase in the brake fluid pressure within the closed portion causes the locations where tooth tips of the internal tooth portion of the outer rotor and the external tooth portion of the inner rotor come into contact to be pushed open by internal pressure, giving rise to brake fluid leakage around the tooth tips.